The meteor that shocked Russia in February when it exploded in the skies above Chelyabinsk shows us that the danger from space rocks smashing into Earth is much bigger than previously thought, an international group of scientists has concluded.

The 20-meter-wide meteor, which streaked across the sky and
exploded into small pieces on Feb. 15, smashing windows, damaging
buildings and damaging residents’ eyesight, could have caused
much more damage if it had been more solid, three studies
published in US journals Nature and Science on Wednesday found.

After studying the area around the explosion and a wealth of
video and other evidence over the last few months, NASA scientist
Paul Chodas said the meteor blast showed that there were about 20
million space rocks whizzing around the solar system that could
do serious damage to Earth – not the 3 million previously
thought. That’s because it was considered that meteors had to be
30 meters and wider to cause huge devastation, but Chelyabinsk
was actually a nearer miss than it seemed at the time, the
scientists said.

Hundreds of videos recorded by car dashboard cameras were
analyzed, which helped a great deal to verify the exact
trajectory, speed and the energy of the meteor explosion that
shattered windows in more than 3,600 apartment
blocks, broke in doors and gates, in some cases
collapsing roofs and knocking many pedestrians off their
feet.

Over 1,200 people in the Chelyabinsk region were hospitalized
that day because of the nuclear-like explosion.

According to the data now available, the Chelyabinsk meteor was
traveling at a speed of 19 kilometers per second (68,400
kilometers an hour), was about a little bit less than 20 meters
in diameter and weighed about 13,000 tons. Most of it burned up
in the atmosphere and the huge emission of energy at the moment
of the explosion, with no more than 0.05 percent (4-6 tons) of
the debris of the space object reaching the surface of the
planet.

Two groups of scientists published their studies in Nature, one
led by Jirí Borovicka, of the Czech Academy of Sciences, the
second led by Peter Brown, at the University of Western Ontario.
Both calculated that the Chelyabinsk meteor explosion was
equivalent to about 500 kilotons of TNT.

It has also been established that it is highly probable that the
Chelyabinsk meteor was previously a part of a bigger space rock,
two kilometers in diameters – an asteroid identified as (86039)
1999 NC43 that will pass several millions kilometers away from
Earth in March 2014.

Brown’s group estimated the peak brightness of the explosion as
30 times brighter than the sun, which led to many, sometimes
severe, cases of skin burns and eye retinas being damaged, as an
estimated 70 people temporarily lost their sight because of the
bright explosion.

The scientists also concluded that the existing models of
atmosphere meteor explosions, based on nuclear warhead test data,
were not correct, leading scientists to increase the estimated
number of space rocks dangerous for Earth flying around the sun.

NASA previously considered meteorites dangerous if they were more
than 30 meters in diameter on impact with Earth. After the
Chelyabinsk 20-meter meteor exploded with a force of 40 Hiroshima
atomic bombs, it became evident that instead of an estimated 3
million potentially dangerous objects in the solar system,
scientists should keep tabs on 20 million asteroids.

And while such events were expected to occur only once every 150
years, now 30 years looks more likely to be the frequency of such
catastrophes.

The research was based on the work of an international team of 59
researchers from nine countries, led by Olga Popova of the
Russian Academy of Sciences. They collected data from multiple
sources, including data from a world net of subsonic sonars used
by inspectors of the Comprehensive Nuclear-Test-Ban Treaty and
the US military satellites monitoring missile launches and tests,
Gazeta.ru reported.

The scientists calculated the kinetic power of the meteor more
accurately at 590 kilotons, nearly twice the power of a W87
American 300-kiloton thermonuclear warhead.

The group conducted research in the impact zone and modeled of
the meteor explosion’s shock wave, which coincided.

The scientists visited 50 villages around Chelyabinsk within
weeks after the event, mapping the meteor’s destructive
consequences.

They found out that the impact zone spread out as wide as 90
kilometers, resembling a butterfly, making it similar to the
impact zone of another famous meteorite explosion, the Tunguska
meteor that struck on June 30, 1908 above the Siberian taiga. The
Tunguska meteor (a small comet) was up to 150 meters in diameter
and the estimated explosion that happened about 10 kilometers
above the surface was estimated of up to 30 megatons of TNT
equivalent, 100 times more powerful than the Chelyabinsk meteor.

Popova’s group collected answer to over 1,700 questionnaires of
eyewitnesses to the Chelyabinsk phenomenon. People said they
could see traces of the meteor from as far away as 700
kilometers.

Some of the eyewitnesses questioned by the scientists told them
something like, “Huh, I thought Americans were nuking us!”

Popova said the Chelyabinsk meteor was a “standard” LL-type
chondrite, with a relatively small quantity of iron in it. But it
is still magnetic, and it can be easily detected by a mine
detector and rusts when it comes into contact with water, Popova
said.

As a rule meteors lose about 90 percent of their mass while they
travel through Earth’s atmosphere, but the one that exploded over
Chelyabinsk practically disappeared, Popova said. The largest
peace of space rock retrieved from Lake Chebarkul in October
weighs 570 kilograms, compared to the meteor’s originally
estimated 18,000 tons.

“That’s why we still don’t know what destructive forces space
bodies are exposed to when they enter the atmosphere,” Olga
Popova told Gazeta.ru.